Eccentric screw pump

ABSTRACT

The invention relates to an eccentric screw pump ( 100 ), in particular for conveying viscous, highly viscous and abrasive media, having a longitudinal direction L, having a conical, helically wound, at least single-start rotor ( 1 ) having a gradient h, having at least one eccentricity (e 1 , e 2 , e 3 , . . . e n ) and at least one cross-section d that is rotatably arranged in a single or multi-start conical stator ( 2 ) wherein a plurality of chambers ( 3, 4, 5 .  . . n) each having a volume (V 3 , V 4 , V 5 . . . V n ) is formed between the rotor ( 1 ) and stator ( 2 ) that serve to convey the medium and wherein the chambers ( 3, 4, 5 . .  . n) between the stator and the rotor arc limited by a sealing line D. The volumes (V 3 , V 4 , V 5  . . . V n ) of each individual chamber ( 3, 4, 5 . . .  n) between the stator ( 2 ) and the rotor ( 1 ) are equal.

The invention relates to an eccentric screw pump, in particular for conveying viscous, highly viscous and abrasive media, having a longitudinal direction L, exhibiting at least one conical, helically wound, at least single-start rotor having a pitch h, having at least one eccentricity e and at least one cross-section d that is rotatably arranged in a single or multi-start conical stator, wherein a plurality of chambers each having a volume is formed between the rotor and the stator that serve to convey the medium, and wherein the chambers between the stator and the rotor are delimited by a sealing line D. Furthermore, the invention relates to an eccentric screw pump, in particular for conveying viscous, highly viscous and abrasive media, having a longitudinal direction L, exhibiting at least one stepped, helically wound, at least single-start rotor having a pitch h, having at least one eccentricity e and at least one cross-section d that is rotatably arranged in a single or multi-start stepped stator.

Eccentric screw pumps are known sufficiently from the state-of-the-art; for example, DE 633,784 describes an eccentric screw pump in which two helical elements are intertwined and where the outer element has one more worm thread or tooth than the inner element and where the pitches of the worm threads of the two elements behave like the thread or tooth numbers, however being either constant or increasing or decreasing, whereby at least three interacting spiral-shaped elements are provided, of which the middle one has one tooth more than the inner one and one tooth less than the outer one.

Known from DE 27 36 590 A1 is an eccentric screw pump with a conical screw shaft and a housing insert, which is characterized by the fact that the eccentric screw shaft has a round, cylindrical base cross-section and a conically increasing tapered outer diameter, and that the conically wound, inner hollow screw with twice the pitch of the eccentric screw shaft causes a tapered hypocycloidal rolling off on the eccentric screw shaft on the inside surface of the conical, wound hollow screw.

The problem with the eccentric screw pumps of the prior art is that so-called cavitations may occur with eccentric screw pumps that exhibit multiple chambers, caused by signs of wear during pump operation through increases in the chamber volume, which results in the conveying capacity of such eccentric screw pumps no longer being optimal.

Based on this problem, it is the objective of the present invention to provide an eccentric screw pump that can be adjusted easily in case of wear, such that an optimum pump performance can be expected at all times and a replacement of the stator and/or rotor is required less often.

To solve the problem, the eccentric screw pump according to the invention is characterized by the fact that the volumes of each chamber between stator and rotor are equal in size.

This inventive design of an eccentric screw pump makes it possible that the pump will always exhibit the maximum possible conveying capacity. If there are any signs of wear, the rotor shaft and/or the stator can, for example, be moved in the longitudinal direction such that the chamber volumes are again equal and the pumping performance of the eccentric screw pump is optimal.

The invention provides that the cross-section d of the rotor decreases in the longitudinal direction of the rotor. A constant chamber volume can be maintained via the decrease of the cross section, for example, with a changing change of the eccentricity.

In addition, other embodiments are possible, namely that the pitch h of the rotor decreases with a decreasing cross-section d of the rotor and that the rotor exhibits a decreasing cross-section d in the longitudinal direction L. It is also possible that the eccentricity e of the rotor increases or decreases in the longitudinal direction L and that the cross-section d of the rotor decreases or increases. Furthermore, the eccentric screw pump according to the invention can be designed such that the eccentricity of the rotor increases or decreases in the longitudinal direction and the pitch h of the rotor increases or decreases in the longitudinal direction.

It is also possible that in an eccentric screw pump according to the invention, the eccentricity of the rotor increases or decreases in the longitudinal direction L, the pitch h of the rotor increases or decreases in the longitudinal direction L and that the rotor exhibits a decreasing or increasing cross-section d in the longitudinal direction. Through varying the parameters described above, the pumping performance of the eccentric screw pump according to the invention can be optimized further, or adapted to the respective requirements as specified based on the goods to be conveyed, for example.

In addition, due to these variation options it is possible to provide eccentric screw pumps for various fields of application, namely applications where viscous, highly viscous and/or abrasive media must be transported.

To increase the service life of the eccentric screw pump according to the invention, the rotor may exhibit a coating containing chrome, for example, with a ceramic material or other materials for wear protection.

The invention provides that the stator and/or rotor may be made of an elastomeric or a solid material. Here too the option exists to provide the respective material for the stator and/or rotor of the eccentric screw pump according to the invention depending on the intended application.

Advantageously, the stator may also exhibit a ring or tube-shaped stator shell that is made of a different material. This stator shell can be employed to protect the stator and thus to increase the service life of the eccentric screw pump.

Advantageously, such a stator exhibits a tapered shape.

According to the invention, it is further provided that the stator has a uniform plastic wall thickness.

An embodiment of the invention shall be explained in greater detail based on a drawing. The Figures show:

FIG. 1 a the longitudinal section through the rotor of an eccentric screw pump according to the invention;

FIG. 1 b the view of the rotor of an eccentric screw pump according to the invention at position A;

FIG. 1 c an additional view of a rotor of an eccentric screw pump according to the invention at position B;

FIG. 2 the longitudinal section through an eccentric screw pump according to the invention;

FIG. 3 a the longitudinal section through an additional embodiment of the eccentric screw pump according to the invention;

FIG. 3 b the view of the rotor of an eccentric screw pump according to the invention at position A;

FIG. 3 c the view of the rotor onto the rotor of an eccentric screw pump according to the invention at position B;

FIG. 4 a the longitudinal section through rotor and stator of an eccentric screw pump according to the invention;

FIG. 4 b the view of an eccentric screw pump according to the invention at position A;

FIG. 4 c the view of an eccentric screw pump according to the invention at position B;

FIG. 5 a the longitudinal section through an eccentric screw pump according to the invention of an additional embodiment;

FIG. 5 b the view of an eccentric screw pump according to the invention at position A;

FIG. 5 c the view of an eccentric screw pump according to the invention at position B;

FIG. 6 a the longitudinal section through an additional embodiment of the eccentric screw pump according to the invention;

FIG. 6 b the view of an eccentric screw pump according to the invention at position A;

FIG. 6 c the view of an eccentric screw pump according to the invention at position B;

FIG. 7 a the longitudinal section through an additional embodiment of an eccentric screw pump according to the invention;

FIG. 7 b the view of an eccentric screw pump according to the invention at position A; and

FIG. 7 c the view of an eccentric screw pump according to the invention at position B.

FIG. 1 shows a rotor 1 of an eccentric screw pump according to the invention in a longitudinal section. The rotor 1 exhibits a pitch h as well as an eccentricity e₁ at the beginning of the rotor 1 and an eccentricity e_(n) at the end of the rotor 1. In the longitudinal direction L of the rotor 1 the eccentricity of the rotor 1 increases such that the dimension e_(n) is greater than the dimension e₁. FIG. 1 b shows the view A:A onto the beginning of the end of the rotor 1. The rotor 1 exhibits a cross-section d₁ and the eccentricity e₁, which is recognizable in this view as well. FIG. 1 c shows the view B:B of FIG. 1 a, in which it is apparent that the cross-section d_(n) at the end of the rotor 1 is smaller than the cross-section d₁ at the beginning of the rotor 1. It is also recognizable that the eccentricity increases in the longitudinal direction L of the rotor 1.

FIG. 2 shows the stator 2 of an eccentric screw pump according to the invention. The previously described rotor 1 of FIG. 1 a can be inserted into this stator 2, thus forming the eccentric screw pump according to the invention, which is characterized in that the individual volumes that are available for transporting the medium are equal in size in the longitudinal direction L of the rotor. The longitudinal view of FIG. 2 clearly demonstrates the tapering of the stator as well as that of the rotor, which fits into said stator. Due to the tapering of stator 2 and rotor 1 and the respective settings of pitch, cross-section and/or eccentricity, it is possible to keep the individual volumes of the chambers located in the eccentric screw pump according to the invention constant.

FIGS. 3 a, 3 b and 3 c show a further embodiment of a rotor 1, which can be inserted into an eccentric screw pump according to the invention. At its beginning (view A:A), the rotor 1 exhibits a cross-section d₁, which is larger than the cross-section of the rotor 1 at its end (view B:B) and is designated with d₂. A decrease in the cross-section of rotor 1 resulting in a conical shape of the rotor 1 can be recognized along the longitudinal direction L of the rotor 1. The eccentricity e of the rotor begins at the start of the rotor 1 (position A) with a size of e₁ and ends at position B with a maximum value of e_(n). Thus, the eccentricity e increases in the longitudinal direction of the rotor 1, i.e., from the larger cross-section to the smaller cross-section d. FIGS. 3 b and 3 c show the respective views A:A and B:B that enable the top view onto the end or the beginning, respectively of the rotor 1. From FIG. 3 b it can be seen that the eccentricity e₁ at the beginning of the rotor 1, at the location A with the cross-section d₁ is clearly smaller than the eccentricity e_(n), which is visible in FIG. 3 c presenting a view (view B:B) onto the end of the rotor. FIG. 3 c also demonstrates that the cross-section d₂ is smaller than the cross-section d₁ as well.

Shown in FIG. 4 a is an eccentric screw pump 100 according to the invention that exhibits a rotor 1 and a stator 2. Various chamber volumes V₃, V₄, V₅ . . . V_(n) of the chambers 3, 4, 5 . . . n, all of which are of the same size can be recognized between rotor 1 and stator 2. The equal size of the volumes listed above is a result of the fact that the rotor 1 exhibits both a predetermined tapering and an eccentricity, pitch and/or cross-section of the rotor 1 adapted to it, said rotor being surrounded by a correspondingly shaped stator 2. In order to have a liquid abrasive and/or highly viscous medium transported by the eccentric screw pump 100, a sealing line D is formed between the stator 2 and the rotor 1, along which the necessary pressure is generated that is necessary to transport the abrasive, highly viscous medium under pressure through the eccentric screw pump 100. Due to the rotational movement of the rotor 1 said sealing line moves essentially in the form of a spiral along the longitudinal direction L in the direction of the outlet of the eccentric screw pump 100 according to the invention and moves the medium to be transported in the direction of the pump outlet. The medium to be transported, which is located within the volumes, is moved in the direction of the outlet of the eccentric screw pump 100 according to the invention. The eccentric screw pump 100 according to the invention can be driven, for example, by an electric motor that is located at the end (position A) of the eccentric screw pump according to the invention, which exhibits the cross-section d₁ and turns the rotor 1 at this location. Also apparent from FIG. 4 a is the fact that the cross-section d₁ at the beginning of the rotor 1 is greater than the cross-section d₂ at the end of the rotor 1. This entails that the eccentricity of the eccentric screw pump 100 according to the invention at the beginning, i.e., in the region of the inlet into the eccentric screw pump (position A) is smaller than at the end (position B), i.e., towards the outlet end of the medium of the eccentric screw pump 100. The eccentricity at the inlet of the eccentric screw pump (position A) is designated with e₁ and the eccentricity at the outlet (position B) of the eccentric screw pump 100 according to the invention is designated with e_(n). The views onto the inlet region or the outlet region, respectively, of the eccentric screw pump 100 according to the invention, which are shown in FIGS. 4 b and 4 c also indicate once more clearly that the eccentricity in the longitudinal direction L of the eccentric screw pump 100 according to the invention, or in the longitudinal direction L of the rotor 1, respectively, increases such that e₁ is smaller than e_(n). Accordingly, the cross-section d₁ at the beginning of the rotor is greater than the cross section d₂ of the rotor 1 in the end region of the eccentric screw pump 100. FIGS. 4 a to 4 c show an eccentric screw pump 100 for which both the cross-section of the rotor 1 and the eccentricity e of the rotor 1 have been changed.

FIGS. 5 a to 5 c show a further possible embodiment of the eccentric screw pump 100 according to the invention, which differs from the eccentric screw pump 100 shown in FIGS. 4 a to 4 c in that the cross-section d₁ of the rotor 1 is not altered in the longitudinal direction L of the rotor 1. In order to still keep the volumes V₃, V₄, V₅, to V_(n) at an equal size, the pitch h of the rotor or of the stator, respectively has been changed in this embodiment of an eccentric screw pump 100 according to the invention in the longitudinal direction L of the eccentric screw pump according to the invention. In particular, FIG. 5 a shows that the pitch h decreases in the longitudinal direction L of the eccentric screw pump 100 according to the invention. FIGS. 5 b and 5 c show the views along the line A:A or B:B, respectively from FIG. 5 a, namely the views onto the inlet end or the outlet end, respectively, of this embodiment of the eccentric screw pump 100 according to the invention. It becomes apparent that the eccentricity e₁ at the inlet end of the eccentric screw pump is greater than the eccentricity e_(n) in the outlet region. FIGS. 6 a to 6 c also show a further embodiment of the eccentric screw pump 100 according to the invention, which differs from the eccentric screw pump shown in FIGS. 4 a to 4 c in that in this embodiment, both the cross-section and the pitch of the rotor or the stator, respectively, were changed.

In particular, FIGS. 6 b and 6 c demonstrate that the cross-section of rotor 1 in the inlet region of the eccentric screw pump is greater than the cross-section of rotor 1 in the outlet region of the eccentric screw pump.

FIGS. 7 a to 7 c show a further variant of the eccentric screw pump according to the invention, in which the eccentricity, the diameter and the pitch of the rotor or stator, respectively, were changed, with the individual volumes V₃, V₄, V₅ being held constant. In particular, FIG. 7 a demonstrates that the pitch h decreases in the longitudinal direction L of the eccentric screw pump according to the invention. The change in terms of the cross section of rotor 1 and the eccentricity e are shown in FIGS. 7 b and 7 c.

LIST OF REFERENCE NUMBERS

-   100 Eccentric Screw Pump -   1 Rotor -   2 Stator -   3 Chamber -   4 Chamber -   5 Chamber -   n Chamber -   e₁ Eccentricity -   e₂ Eccentricity -   e₃ Eccentricity -   e_(n) Eccentricity -   V₁ Volume -   V₂ Volume -   V₃ Volume -   V_(n) Volume -   L Longitudinal direction -   h Pitch -   d Cross-section 

1. An eccentric screw pump (100), in particular for conveying viscous, highly viscous and abrasive media, having a longitudinal direction L, exhibiting at least one conical, helically wound, at least single-start rotor (1) having a pitch h, having at least one eccentricity (e₁, e₂, e₃, . . . e_(n)) and at least one cross-section d that is rotatably arranged in a single or multi-start conical stator (2), wherein a plurality of chambers (3, 4, 5 . . . n) each having a volume (V₃, V₄, V₅. . . V_(n)) formed between the rotor (1) and the stator (2) that serve to convey the medium, wherein the chambers (3, 4, 5 . . . n) between the stator (2) and the rotor (1) are delimited by a sealing line D, characterized in that the volumes (V₃, V₄, V₅ . . . V_(n)) of each chamber (3, 4, 5 . . . n) between stator (2) and rotor (1) are equal in size.
 2. An eccentric screw pump, in particular for conveying viscous, highly viscous and abrasive media, having a longitudinal direction L, exhibiting at least one stepped, helically wound, at least single-start rotor having a pitch h, having at least one eccentricity e and at least one cross-section d that is rotatably arranged in a single or multi-start stepped stator, wherein a plurality of chambers each having a volume formed between the rotor and the stator that serve to convey the medium, wherein the chambers between the stator and the rotor are delimited by a sealing line D, characterized in that the volumes of each chamber between stator and rotor are equal in size.
 3. An eccentric screw pump (100) as set forth in claim 1 or 2, characterized in that the pitch h of the rotor (1) decreases in the longitudinal direction L of the rotor (1).
 4. An eccentric screw pump (100) as set forth in claim 1 or 2, characterized in that the rotor (1) exhibits a protective coating containing chrome, with a ceramic material or other materials for wear protection.
 5. An eccentric screw pump (100) as set forth in one of the claims 1 to 4, characterized in that the pitch h of rotor (1) decreases with a decreasing cross-section d of the rotor (1) and that the rotor (1) exhibits a decreasing cross-section d in the longitudinal direction L.
 6. An eccentric screw pump (100) as set forth in one of the claims 1 to 4, characterized in that the eccentricity (e₁, e₂, e₃, . . . e_(n)) of the rotor (1) increases or decreases in the longitudinal direction L and the cross-section d of the rotor (1) decreases or increases.
 7. An eccentric screw pump (100) as set forth in one of the claims 1 to 4, characterized in that the eccentricity (e₁, e₂, e₃, . . . e_(n)) of the rotor (1) increases or decreases in the longitudinal direction L and the pitch h of the rotor (1) increases or decreases in the longitudinal direction L.
 8. An eccentric screw pump (100) as set forth in one of the claims 1 to 4, characterized in that the eccentricity (e₁, e₂, e₃, . . . e_(n)) of the rotor (1) increases or decreases in the longitudinal direction L, the pitch h of the rotor (1) increases or decreases in the longitudinal direction L, and in that the rotor (1) exhibits a decreasing or increasing cross-section d in the longitudinal direction L.
 9. An eccentric screw pump (100) as set forth in one or more of the previous claims, characterized in that the stator (2) and/or the rotor (1) is made of an elastomeric or a solid material.
 10. An eccentric screw pump (100) as set forth in one or more of the previous claims, characterized in that the stator (2) exhibits a ring or tube-shaped stator shell that is made of a different material.
 11. An eccentric screw pump (100) as set forth in claim 10, characterized in that the stator shell exhibits a tapered shape.
 12. An eccentric screw pump (100) as set forth in one or more of the previous claims, characterized in that the stator (2) exhibits a uniform plastic wall thickness. 